configs: net: dm9000: Move new Kconfig option to board configs

Drop legacy #define CONFIG_DRIVER_DM9000 from board include/configs/
and enable the same in Kconfig configs/ .

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Joe Hershberger <joe.hershberger@ni.com>
Cc: Ramon Fried <rfried.dev@gmail.com>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>
diff --git a/configs/at91sam9261ek_nandflash_defconfig b/configs/at91sam9261ek_nandflash_defconfig
index 20909d8..36677c7 100644
--- a/configs/at91sam9261ek_nandflash_defconfig
+++ b/configs/at91sam9261ek_nandflash_defconfig
@@ -51,6 +51,7 @@
 CONFIG_DM_SPI_FLASH=y
 CONFIG_SPI_FLASH_ATMEL=y
 CONFIG_SPI_FLASH_DATAFLASH=y
+CONFIG_DRIVER_DM9000=y
 CONFIG_PINCTRL=y
 CONFIG_PINCTRL_AT91=y
 CONFIG_DM_SERIAL=y